ASLA Green Roof

Your Guide

The green roof at ASLA headquarters is an excellent example of green infrastructure – a landscape that nurtures as it nourishes. It is infrastructure in that it is literally the roof over the heads of ASLA staff. Designed by Michael Van Valkenburgh Associates, the green roof nurtures, in that it creates a tranquil setting above the city with its enveloping sweeps of groundcovers and perennials, creating a cozy nook in the sky. It nourishes in that it collects and cleanses rain water prior to releasing it into its watershed demonstrating the ecological service provided by landscape.

These sloping meadows belie the fact that the depth of soil does not exceed 18 inches due to structural limitations. Lightweight Styrofoam fill makes up the base of the pair of mounds. The effect is stunning – shaping a space, focusing views, and allowing the plantings to be seen from the street below.

An interesting facet of the design is the use of metal grating for the floor material. If you look closely, you will see that groundcovers are growing beneath this porous pavement, nourished by rain water that flows right through the deck.

The South Mound

Detail of planting on the south mound shows the use of cactus as one of the plants, located at the crest of the mound where soil moisture is least.

Image: American Society of Landscape Architects

A View from the Street

The north mound is visible from Eye Street below giving passersby a glimpse of the green roof.

Image: American Society of Landscape Architects

Hiding Compressors and Heat Pumps

The south mound screens compressors and heat pumps that occupy the rear of the roof area.

Image: American Society of Landscape Architects

A Diversity of Plant Life

Detail of the north mound shows the diversity of plants and how it sweeps up toward Eye Street to be visible from the street below.

Image: American Society of Landscape Architects

Deck Materials

Detail of deck materials of wood and steel. Note that groundcovers are planted underneath the steel decking so that material acts as a form of porous paving.

Image: American Society of Landscape Architects

A Destination

The green roof has become a destination for hundreds of visitors annually because of the public access. Note that the stair enclosure itself sports its own small green roof as well.

Image: American Society of Landscape Architects

Seasonal Flowers

Detail of planting shows the rich colors of seasonal flowers.

Image: American Society of Landscape Architects

Sedums

Detail of planting shows delicate texture of sedums.

Image: American Society of Landscape Architects

A Structured System

The mounds of the green roof are shaped by a steel frame wall. While the wall is up to 4 feet high, the soil depth within never exceeds 18 inches because of structural limitations. The remainder of the space is occupied by lightweight styrafoam fill.

Image: American Society of Landscape Architects

The Central Deck

The green roof consists of a central deck with seating and a pair of sloping mounds that frame the view. The stairs were added to the roof as part of the project scope to allow the public to visit.